The invention relates generally to fluid pumping apparatus. More particularly, the preferred embodiment of the invention relates to apparatus to obtaining liquid samples from a well or the like.
Recent increases in public concern for the environment have resulted in various government-imposed environmental regulations. Among such regulations are requirements relating to the monitoring of groundwater quality. In response to these requirements, water quality analytic capabilities have been improved and water sampling equipment has been developed. Much of the previously-developed sampling equipment has not been effective, however, in obtaining consistent, non-contaminated water samples that are accurately representative of the water system from which the sample is taken.
The inadequacies of previous sampling equipment stem largely from such causes as cross-contamination between sampling sites, ineffective and inconsistent field cleaning methods, contamination due to equipment handling, and inconsistent well depth sampling. In addition to presenting sample quality problems, much of the previous equipment has been heavy and bulky and thus difficult to transport from one monitoring site to another. Finally, much of such previous equipment has proved to be complicated to operate, inordinately expensive, and impractical for sampling at remote locations where site access is severely limited.
In accordance with the present invention, a fluid sampling apparatus is provided for use in obtaining accurate samples of groundwater or other fluids. In the preferred embodiment, the pump is dedicated to a particular monitoring well or other sampling site in order to substantially avoid cross-contamination of samples from site-to-site and is constructed from lightweight, non-contaminating materials.
The preferred sampling pump is a submersible, fluid-actuated pump wherein the actuating fluid is preferably a gas. A flexible bladder member separates and isolates the interior of the pump into two chambers; a first chamber that contains the sample fluid and is in communication with both the pump inlet and outlet, and a second chamber that surrounds the first chamber, with the bladder disposed therebetween, and that is connected to a source of the actuating gas. The sample fluid is conveyed through the pump by alternately pressurizing and venting or relieving the pressure in the second chamber to contract and relax the bladder member, thus alternately decreasing and increasing the volume of the first chamber. Sample fluid is drawn into the first chamber during such increases in volume under the influence of the natural hydrostatic head of the groundwater and is discharged through the pump outlet during such decreases in volume, thereby conveying the sample fluid through the pump. The components of the pump are preferably composed of low-cost, lightweight synthetic materials that are non-corrosive and do not otherwise affect the chemical composition of the sampled fluid.
The sampling pump is preferably dedicated to, and thus remains in, a particular sampling site or well, which is substantially isolated from the above-ground surroundings by a wellhead assembly in order to reduce potential contamination during sampling. A portable controller apparatus is provided with quick connect-disconnect means and includes means for alternately pressurizing and de-pressurizing the actuating fluid. The fluid sampling apparatus may also optionally include means for measuring the standing level of the fluid in the well.
Additional advantages and features of the present invention will become apparent from the following description and the appended claims taken in conjunction with the accompanying drawings.